Johnson, Kenneth Gregory, Robert W. Duncan, and Michael R. Pelton. Reproductive Biology of European Wild Hogs in the Great Smoky Mountains National Park In The Southeastern Association of                        Fish and Wildlife Agencies Annual Conference Proceedings., 1982.

Duncan, Robert W.. Reproductive Biology of the European Wild Hog (Sus scrofa) in the Great Smoky Mountains National of Tennessee. Vol. Master of Science. Knoxville, Tenn.: The University of Tennessee, 1974.